TOMATO FRUIT LIPOXYGENASE - ISOLATION, PARTIAL-PURIFICATION, CHARACTERIZATION, AND INTERACTION WITH BIOLOGICAL-MEMBRANES

A method has been developed for the purification of lipoxygenase from tomato fruits. When measured in the presence of sodium cholate, the ac tivity of the isolated enzyme was optimal at pH 5.8. In the absence of the detergent the optimum was detected at pH 6.8. The value of K-m, d etermined for the enzyme with linoleic acid as substrate, was 9.0 mu M . The following series was formed if conventional lipoxygenase substra tes were arranged in order of decreasing conversion rate: 9, 12-octade cadienoate (100%) > 9, 12, 15-octadecatrienoate (91%) >> 6,9,12-octade catrienoate (24.4%) > 5,8,11,14-eicosatetraenoate (15.2%) > 11,14,17-e icosatrienoate (8%) > 11,14-eicosadienoate (3.4%). The lipoxygenase wa s shown to interact with the membranes of mitochondria and chloroplast s. The interactions resulted in oxygen consumption and inhibition of t he electron-transporting NADH oxidase system.